Growing environmental consciousness and a corresponding body of law place ever-increasing emphasis on maintaining water quality in lakes, streams, and groundwater. Due to this emphasis, there is a growing market for systems capable of monitoring various physical and chemical properties of water resources. A sampling of the parameters of interest includes conductivity, dissolved-oxygen concentration, oxygen-reduction potential (ORP), pH, temperature, depth, and specific ion concentrations.
Surface-water data is typically collected using immersed sensors. Collecting groundwater data can be more troublesome, often requiring that wells be drilled for sensor insertion. Drilling wells is expensive, but minimizing bore diameter can reduce the cost. Sensors for use in wells are therefore made to have relatively small diameters. For a detailed description of typical sensors, see U.S. Pat. No. 6,305,944 to Henry et al., which is incorporated herein by reference.
While smaller sensor systems are desirable from the end-user""s perspective, smaller systems are generally more difficult and expensive to build and maintain. There is therefore a need for small, reliable sensor systems that are easily assembled and maintained.
FIG. 1 (prior art) is an exploded view of a system 100 that can be adapted for monitoring water quality in e.g. lakes, rivers, ponds, tanks, and groundwater. System 100 is detailed in U.S. Pat. No. 6,331,117 B1 issued to Gary L. Brundage, which is incorporated herein by reference.
System 100 includes a pair of circuit modules 110 and 120 disposed between connector supports 125 and 130, respectively. Module 120 includes printed circuit boards 122A and 122B each having respective integrated circuits 124A and 124B. A conductive member 135 is disposed between wiring boards 140A and 140B of respective circuit modules 110 and 120. System 100 is completed when a component housing 145, typically a stainless-steel tube, is threaded onto each of connector supports 125 and 130. A pair of dimples 150 and 155, pressed into the side of component housing 145, create corresponding protrusions on the inside surface of component housing 145. These protrusions mate with threads 160 and 165 to secure respective connector supports 125 and 130 to component housing 145. As compared with other types of machine threads, dimples 150 and 155 are relatively easily and inexpensively formed.
Once system 100 is assembled, spring 170 exerts a compressive force on a stack of circuit components, including circuit modules 110 and 120 and conductive member 135. This compressive force ensures excellent electrical contact between opposing wiring boards (e.g., boards 140D and 140E).
Each circuit module 110 and 120 can be virtually any type of electrical circuit. Being arranged as they are, components 110 and 120 can be removed and replaced as easily as batteries in a flashlight. Moreover, component housing 145 can be substituted with a longer or shorter housing to accommodate more or fewer electrical components or to accommodate components of different sizes. Dummy components can be inserted to allow room for future additions. For example, a particular system may be adapted for use where no power supply is readily available by substituting a dummy component with a battery-pack module.
System 100 can support a number of applications. Sensor 175 may be, for example, an ion sensor for monitoring ground water, a thermometer, a microphone, a video camera, or any of a variety of other conventional transducers. In one embodiment, sensor 175 is a pH sensor for monitoring groundwater acidity or alkalinity, circuit module 120 is a differential amplifier configured to amplify an output signal from sensor 175, and circuit module 110 is a transmitter that transmits versions of signals received from module 120 via cable 180. This system is easily adapted for used as e.g. a pressure sensor by installing an appropriate pressure transducer/pre-amplifier combination as sensor 175 and module 120. Alternatively, the above-described pH sensor can be adapted to transmit signals in compliance with different communication standards by substituting the module 110 for a different type of transmitter. Many permutations are possible, as will be obvious to those of skill in the art.
The order and orientation of the various modules can be critical to system function. Some systems may therefore include modules that can only be installed in a particular orientation, thus ensuring that the systems cannot be assembled improperly. For example, wiring board 140D of system 100 is smaller in diameter than wiring board 140B so that circuit module 120 cannot contact wiring board 140E should circuit module 120 be installed backwards. For more information and details on system 100, see the above-referenced patent to Brundage.
The modularity of system 100 advantageously reduces required inventory by supporting a large number of common parts among a relatively large number of applications. This advantage is further enhanced by the system""s ease of assembly: instead of having a fixed number of each of many types of sensors on hand to fill orders quickly, a manufacturer can fill a particular customer requirement from stock by combining appropriate modules. Despite these advantages, there is an ever-present demand for systems and methods that speed assembly and otherwise improve manufacturability without sacrificing quality or performance.